Production of 3-methylbut-2-en-1-ol or 3-methylbut-2-en-1-yl acetate

ABSTRACT

PRODUCTION OF 3-METHYLBUT-2-EN-1-01 AND 3 METHYLBUT2-EN-1-YL ACETATE BY ISOMERIZING 3-METHYL-3-BUTEN-1-01 OR 3-METHYL-3-BUTEN-1-YL ACETATE WITH A CATALYTIC AMOUNT OF A CARBONYL COMPOUND OF A METAL OF SUBGROUPS 6 TO 8 OF THE PERIODIC SYSTEM.

United States Patent US. Cl. 260-491 2 Claims ABSTRACT OF THE DISCLOSUREProduction of 3-methylbut-2-en-l-ol and 3-methylbut- 2-en-1-yl acetateby isomerizing 3-methyl-3-buten-1-ol or 3-methyl-3-buten-1-yl acetatewith a catalytic amount of a carbonyl compound of a metal of subgroups 6to 8 of the Periodic System.

The present invention relates to a new process for the production of3-methylbut-2-en-1-ol or 3-methylbut-2-enl-yl acetate.

It is known that these compounds (also known as prenol and prenylacetate) can be prepared in a multistage synthesis. This method istroublesome however and gives only unsatisfactory yields.

We have now found that 3-methylbut-2-en-1-ol or 3- methylbut-Z-en-l-ylacetate can be obtained in a simple way and in high yields by treating3-methylbut-3-en-1-ol or 3-methylbut-3-en-1-yl acetate with a catalyticamount of a carbonyl compound of a metal of subgroups 6 to 8 of thePeriodic System.

The starting compounds are known and obtainable particularlyadvantageously by reaction of isobutene with formaldehyde followed ifnecessary by acetylation.

Suitable compounds which act as isomerization catalysts are particularlythose of zerovalent metals in accordance with the definition, moreparticularly, complexes having one or two central atoms such as chromiumhexacarbonyl, iron pentacarbonyl, diiron nonacarbonyl, and nickeltetracarbonyl. Compounds in which some of the carbonyl groups have beenreplaced by other ligands, as in dihydrogen iron tetracarbonyl orhydrogen cobalt tetracarbonyl, are also suitable.

Other suitable ligands in such compounds are those which bear basicnitrogen or phosphorus atoms. Examples of such carbonyl compounds arebistriphenylphosphine iron tricarbonyl and tripyridine diirontetracarbonyl.

Iron pentacarbonyl is particularly preferred as the catalyst.

The amount of carbonyl compound required for the isomerization is from0.01 to 20% by weight, preferably from 1 to by weight, with reference tothe amount of starting material to be isomerized. It is possible howeverto use larger or smaller amounts of these catalysts, the isomerizationmerely being accelerated or retarded thereby.

The reaction may be carried out at temperatures of from about 100 to 300C., preferably from 150 to 200 C. at atmospheric pressure or atsuperatmospheric pressure up to about 50 atmospheres with or without asolvent and batchwise or continuously.

We have further found that particularly good results are obtained in theprocess by carrying out the reaction in the presence of catalyticamounts of a base or a compound having a basic reaction.

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Suitable basic compounds include, in addition to inorganic bases such assodium hydroxide, barium hydroxide or ammonia and in addition to thesalts of strong bases and weak acids such as sodium carbonate orammonium carbonate, particularly nitrogenous basic compounds such asalkylamines or arylamines and also compounds which are capable ofsplitting ofl bases, such as piperidine acetate or acid amides such asacetamide or urea. Basic compounds of phosphorus, such as alkyl and arylphosphines, for example triphenyl phosphine, are also suitable.

Hexamethylenetetramine (urotropine) is preferred as the basic compound.

The presence of basic compounds causes a more rapid and more specificisomerization in the desired direction, i.e. from the 3-ene compound tothe isomeric 2-ene compound. Since there is one more possibility ofisomerization with the free alcohol than with the acetate (namely toisovaleraldehyde), the addition of base is particularly advantageous inthe rearrangement of 3-methylbut-3-en-1-ol to 3-methylbut-2-en-1-ol.

The basic compound is generally used in an amount of from 0.01 to 20%,preferably from 1 to 10%, by weight with reference to the compound to beisomerized.

Hydrocarbons which are liquid under the reaction conditions concerned,as for example hexane, heptane, ligroin, benzene, toluene or xylene, areespecially suitable as solvents. Moreover, high boiling point ether'suchas diphenyl ether, 2,2'-dimethoxydiethyl ether and 2,2'-diet.hoxydiethylether are also suitable.

Since both the starting compounds and the products of the process aresensitive to oxygen, it is advisable to carry out the reaction whileexluding oxygen, for example under nitrogen or argon. When readilydecomposable carbonyl compounds are used as isomerization catalysts, itmay be advantageous to use carbon monoxide.

When the isomerization is over, the reaction mixture may be worked up byconventional methods, preferably by distillation.

The products of the process are valuable intermediates for organicsynthesis, particularly for the production of compounds of thecarotenoid and vitamin A series and of perfumes.

The invention is illustrated by the following examples.

EXAMPLE 1 A mixture of 50 g. of 3-methylbut-3-en-l-yl acetate and 3.5 g.of iron pentacarbonyl is heated for fifteen hours at 150 C. and thedesired product (3-methylbut-2-en-1-yl, B.P. to 112 C. at 200 mm.) isisolated from the mixture in the usual way by fractional distillation.The yield of pure products is 86% at a conversion of 42%.

EXAMPLE 2 A mixture of 2000 g. of 3-methylbut-3-en-1-ol and 10 g. ofiron pentacarbonyl is heated for four hours at C. and from the mixturethe desired product is isolated in the usual way by fractionaldistillation (3-methylbut-2- en-l-ol, B.P. 102 to 105 C. at 200 mm.; n=1.4408). The yield of pure product is 63% at a conversion of 34%.

EXAMPLE 3 A mixture of 1000 g. of 3-methylbut-3-en-1-ol, 10 g. of ironpentacarbonyl and 50 g. of urotropine is heated for ninety minutes at200 C. and the desired product is isolated from this mixture in theusual way by fractional distillation. The yield of pure3-methylbut-2-en-1-ol (B.P. 102 to 105 C. at 200 mm.; n =1.4408) is 75%at a conversion of 50%.

EXAMPLE 4 A mixture of g. of 3-methylbut-3-en-1-ol, 22 g. of ironpentacarbonyl and 9 g. of urotropine is heated for thirty minutes at 200C. and B-methylbut-Z-en-l-ol is isolated in the usual way by fractionaldistillation. The yield of pure product is 89% at a conversion of 31%.

EXAMPLE 5 A mixture of 1000 g. of 3-methylbut-3-en-1-ol, 15 g. of ironpentacarbonyl and 60 ml. of liquid ammonia is heated at 175 C. in anautoclave for two hours and the 3-methylbut-2-en-1-ol is then isolatedby fractional distillation. The yield of pure product is 73% at aconversion of 40%.

EXAMPLE 6 1. An isomerizing process for the production of3-methylbut-Z-en-l-ol or 3-methylbut-2-en-1-y1 acetate which comprisestreating 3-methylbut-3-en-1-ol or 3-methyl-3-enl-yl acetate at atemperature of about 100 C. to 300 C. with a catalytic amount of ironpentacarbonyl and in the presence of a catalytic amount of a basicreacting compound selected from the class consisting of sodiumhydroxide, barium hydroxide, ammonia, sodium carbonate, ammoniumcarbonate, piperidine acetate, acetamide, urea, alkyl and aryl aminesand phosphines.

2. A process as claimed in claim 1 wherein said basic reacting compoundis hexamethylenetetramine.

References Cited UNITED STATES PATENTS 3,344,191 9/1967 Chappell et a1260--586 2,837,577 6/1958 Blaser et al 260-491 LORRAINE A. WEINBERGER,Primary Examiner V. GARNER, Assistant Examiner US. Cl. X.R.

mg UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.5,655,755 Dated April 11 1972 Inventor(s) H 'S Pommer et 8.1

It is certified that error appears in the above-identified patent andthat said Letters Patent are hereby corrected as shownhelow:

Column '1, lines 10 to 11, Claims priority, application Ger-man Mar. 22,1968, P 77 68 023.8" should read Claims priority, applications Germany,Dec. 8, 1967, P 16 43 709.5; Mar. 22, 1968, P 17 68 023.8

Column 3, line 22, claim 1, "3-methyl-3-enshould read YB-methylbut-B-env Signed and sealed this 21st day of November 1972.

'(SEAL) Attest: p I I v EDWARD M.FLETCHER,JH. ROBERT GOTTSCHALKAttesting Officer 7 Commissioner of Patents

